Hydrophilic low-temperature direct bonding of diamond and Si substrates under atmospheric conditions

A monocrystalline diamond substrate was directly bonded with a Si substrate by annealing at low temperatures under atmospheric conditions. These substrate surfaces were functionalized with hydroxyl groups and subsequently bonded by a dehydration reaction. When a diamond (111) substrate was treated with a H2SO4/H2O2 mixture, it generated a direct bonding with an oxygen-plasma-activated Si substrate without significant loss in diamond crystallinity. The proposed bonding technique would contribute to the diamond device fabrication because the high-crystallinity diamond layer can be transferred by the commonly used cleaning process followed by low-temperature annealing under atmospheric conditions. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.